By the way, the "ki" principle is somewhat universal in all martial arts. They may not put it in their name, but the "ki" is an important part of other martial arts as well. They may call it other names, but once you know what it is, you know they talk about the "ki"... The way of using it or to transform it in a physical, martial, discipline is different, depending on the origin, the "vision" of the founder, etc... But the "ki" principle is simply not exclusive to aikido.